Abstract

Condensing boilers achieve high efficiency by recovering latent heat through the condensation of water vapor in exhaust gases, a process strongly dependent on return water temperature. However, the high-temperature water supply commonly used in apartment buildings may limit the potential benefits. To address this limitation, low-temperature water supply has been proposed as an alternative. This study investigated the applicability of low-temperature water supply to individual heating systems in an experimental apartment in South Korea. Boiler performance was compared between low- and high-temperature water supply conditions based on efficiency and operational characteristics. The average boiler efficiency was 84.4% under low-temperature conditions, compared with 78.4% under high-temperature conditions. Although the average return water temperature showed no significant difference between the two cases, operation within the condensing region was observed for 96.3% of the time under low-temperature conditions and 75.6% under high-temperature conditions. As a result, operation within the high-efficiency condensing region (average efficiency of 87%) was more frequently observed under low-temperature conditions, indicating that low-temperature water supply can improve condensing boiler efficiency in apartment buildings with individual heating systems.

Keywords

Boiler efficiency; Condensing boiler; Individual heating system; Low-temperature heating